Fiber Optics Illustrated Dictionary - Part 8 doc

application layer In layered hierarchy network sys-tems, the layer that provides services to the applica-tions programs as in the Open Systems Interconnec-tion [OSI]model or the layer th

Fiber Optics Illustrated Dictionary

interface builder about two years later, which took

aesthetics, utility, and logical linking to

object-ori-ented structures several steps beyond Power

Win-dows, and facilitated graphical creation ofwinWin-dows,

menus, tables, buttons, and much more, providing a

fast and easy way to create an interface and

connect-ing structures that were consistent with the NeXT

application framework An hour with the interface

builder could easily equal two days ofcoding by hand

with a text editor In the 1990s, other desktop

sys-tems began to come out with interface builders, an

idea that has great practical value, especially as

ob-ject-oriented environments became more prevalent

Some authoring systems also function as application

generators, as do some programmable databases If

the software front-end that allows authoring and

da-tabase configuration without programming also

pro-vides an option to save code that can be accessed and

manipulated, usually with a text editor, and to link to

operating system or program structures, then it is a

form of application generator See application

frame-work

application layer In layered hierarchy network

sys-tems, the layer that provides services to the

applica-tions programs (as in the Open Systems

Interconnec-tion [OSI]model) or the layer that runs the

applica-tions themselves, depending upon the network layer

design In OSI, the application layer ensures

avail-ability ofparties, may provide authentication, checks

the available resources, negotiates data, privacy, and

error-checking parameters, and application-level

pro-tocols See Open Systems Interconnection for a chart

that describes layer relationships

application program A very broad, generic term for

almost any user-level computer program That's not

to say that system administrators don't use

applica-tions; they do They just happen to be more

techni-cal applications aimed at a technitechni-cal user level Short,

specific applications that do a single task or a small

number of tasks are sometimes called utilities, such

as a disk utility for formatting disks, or a conversion

utility for changing a TIFF file to a BMP file, or a

copy utility for duplicating disks Application

pro-grams commonly used in telecommunications

in-clude Web browsers, FTP clients, chat clients,

gam-ing clients (such as bridge, chess, Go, and casino

ap-plications), compression/decompression utilities, and

file translation utilities

Application Program Interface API 1 An

interapplication or intervendor interface that provides

a somewhat standardized means of allowing

pro-grams to talk and work together The Apache server

and the Netscape server API are common interfaces

used to implement network applications services In

a competitive environment, API conformance within

consumer products is rarely perfect By making subtle

changes to a specification in an industry-leading

prod-uct, vendors often slow down the competition (e.g.,

faster modems) and create a short business window

during which they are the only company to support a

particular product or specification (i.e., a temporary

monopoly) However, a certain level of adherence to

standards also has competitive advantages in that it

is easier for third party vendors to support a leading product 2 In the XOpen/Architectural Framework Technical Reference Model, the Application Program Interface is one of five basic elements and one oftwo interface types (the other being the External Environ-ment Interface) The API is a specification for the data link between the Application Software and the Ap-plication Platform upon which all the services are pro-vided, thus facilitating portability and interoperability among systems The API includes the semantics, syn-tax, protocols, data structures, and other definitions necessary to ensure compatibility See External En-vironment Interface

Application Service Provider ASP A vendor that distributes software functionality over data networks such as telephone networks, the Internet, or local! wide area networks To get an idea ofwhat this means, think of the different ways in which a person can get voicemail messages The user can get a voicemail modem and set up the mailboxes on the computer and manage the messages that are received after a call comes through to the user's premises, or she or he can get a phone with built-in voicemail capabilities

On the other hand, an ASP, such as the local telephone carrier or a third-party applications phone services provider, can set up a phone line so that if it is busy

or isn't answered within a certain number ofrings, it will be redirected to a voicemail service associated with the carrier's equipment That carrier is thus a voicemail ASP

With the tremendous growth in digital telephony and data services, it is likely that markets for ASPs will grow, especially for services that are not easy for us-ers to set up and manage themselves See ASP Indus-try Consortium, Enhanced Service Provider Application Software Interface ASI A means of working within a common application interface for provision ofISDN-related digital telephony services See North American ISDN Users Forum

Application Specific Fiber Platform ASFP As implemented by Southampton Photonics (SPI), a plat-form comprising core technologies of specialty fiber design and manufacturing, fiber Bragg grating design and fabrication, and amplifier and laser technology ASFP facilitates the volume manufacture of high-performance in-fiber components and subsystems application-specific integrated circuit ASIC A computer chip or small, specialized circuit designed

to enable or enhance a specific type of application

As examples, ASIC video cards have been designed

to drive specialized monitors, ASIC modem cards provide functionality to specialized or enhanced mo-dems, ASIC daughterboards sometimes provide hard-ware support to rendering and ray-tracing applications applications access point AAP In general, an access point is a device or system that allows users to cess a particular type of service An applications ac-cess point is one that permits acac-cess to applications software The access point is usually instituted for the management of resource sharing and/or for security reasons Applications that may be shared through an

cessed or managed by multiple users or collaborative

work applications in which changes and updates are

relayed to the various participants

applications processorA computerized system that

can be integrated with a phone system to add

func-tionality Functions may include voicemail,

Auto-mated Attendant, Call Detail, networking (packet

switching), and others See peripheral device

Applications Technology Satellite programATS

A series (ATS-l, ATS-2, etc.) of satellite launchings

carried out by the U.S National Aeronautics and

Space Administration (NASA) to test payloads and

study space Five of these craft in three

configura-tions were manufactured by Hughes between 1966

and 1969 See Applications Technology Satellite

Pro-gram chart

Applied Computer TelephonyACT A commercial

product from Hewlett-Packard Company for

integrat-ing voice and data analysis technologies onHP

sys-tems The system is used in conjunction with private

branch phone exchanges to record, handle, and

evalu-ate call-relevalu-ated transactions See Hewlett-Packard

APPNSee Advanced Peer-to-Peer Networking

approved circuitSee protected distribution system

approximate discrete Radon transformADRT A

mathematical technique used in situations where

sub-stantial redundancy is expected or encountered See

discrete cosine transform, Fourier transform

APRAmerican Public Radio See Public Radio

In-ternational

APS 1 See Advanced Photo System 2 See

Auto-matic Protection Switching

APTSAssociation of Public Television Stations

AQL acceptable quality level An

industry-estab-lished confidence level

AquaA new, aesthetically appealing, customizable

user interface introduced by Apple Computer with

Mac OS X for PowerPC- and Intel-based platforms

SeeMacOSX

Arsymb.argon See argon

ARABSATA communications satellite placed into orbit in the mid-1980s The ARABSAT System was

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cial interaction for the League of Arab States This effort was extended in 1976 with the founding ofthe Arab Satellite Communication Organization (ARABSAT)

In the early 1980s, the French Aerospatiale was commissioned to manufacture three satellites

ARABSAT lA and IB were launched in the mid-1980s ARABSAT 1Cwas launchedin February 1992 and ARABSAT lA and IB were turned off in 1992 and 1993 ARABSAT lC is expected to be opera-tional until 2002

ARABSAT has control stations at Dirab, Saudi Arabia, and Tunis, Tunisia Telephony and television services are provided, according to International Standards, to the Saudi Arabia and northern Africa geographic region

Aragon, DominiqueIn 1820, Aragon described how

an artificial magnet could be created by winding a coil around a piece of iron or steel that was carrying

an electrical current Soon after, electromagnets were developed

ARAM audio RAM A low-cost, low-grade inte-grated memory chip suitable for digital answering machines and other inexpensive consumer products

aramid, aramid yarnAstrong fibrous material com-monly used to reinforce fiber optic cables, especially those that may be subject to rough treatment such as abrasion by rodents or small pellet shots

Aramid yam is favored for its low weight, flexibil-ity, water resistance, low conductivflexibil-ity, and high strength properties Aramid may be used in several parts ofa cable assembly Most often it is a reinforcing strength member, but it may also provide the mate-rial for the central element in a fiber bundle, and the ripcord used to open cable for attaching connectors

Dupont distributes a type of aramid yarn under the Applications Technology Satellite Program

Satellite Launched Notes

ATS-I 1966 Spin-stabilized synchronous altitude Electronically despun antenna

Stationed over the Pacific Ocean Successfully photographed Earth and provided a presidential communications link for recovery of Apollo II

ATS-2 1967 Gravity gradient stabilized Insufficient thrust resulted in an elliptical

orbit and it lost orbit after only880days

ATS-3 1967 Synchronous orbit Mechanical despun antenna, color camera that

photographed tornados in 1968 and an eclipse of the Sun in 1970

ATS-4 1968 Gravity gradient stabilization in synchronous altitude Failed to reach

intended orbit and lost orbit in 1968, two months after deployment

ATS-5 1969 Synchronous orbit Gravity gradient booms for stabilization didn't

deploy correctly, but some of the experiments were successful Itwas retiredin1984

Fiber Optics Illustrated Dictionary

well-known tradename Kevlar See Kevlar, swelling

tape

Aramid Yarn in Fiber Optic Cable

In a typical fiber optic cable assembly, the aramid

yarn layer(1)provides strength and strain relief It is

often inserted between the outer strength member and

an inner supporting structure, such as a

water-resis-tant tube A ripcord(2)may be provided to make it

easier to peel back the layer in preparation for

add-ing a connector.

ARB 1 Administrative Review Board Established

in 1996 by the U.S Secretary of Labor within the

Department ofLabor 2 Air Resources Board 3 See

all routes broadcast

arcAvery bright electrical discharge across a gap in

a circuit In fiber filament fusion splicers, carefully

controlled, electrode-generated arcs are used to clean

and heat the ends to be spliced so they will fuse into

a continuous light-guiding path See arc lamp; Aryton,

Hertha Marks; fusion splice; Poulsen arc

ARC See Ames Research Center

arc converterA device used to convert direct

cur-rent (DC) into undamped or continuous wave radio

frequency (RF) signals This technology was used in

early radiotelegraphy Many aspects of global radio

communications in the early 191 Os were based upon

this technology See Poulsen arc

arc lampAnelectrical lamp that exploits the

ten-dency of electrons to jump a gap in a circuit, which

can be harnessed to produce an intense light under

certain circumstances It was invented by Sir

Humphrey Davy in the early 1800s and came into

widespread commercial use in the late 1870s when

it was incorporated into street lamps

Arc lamps are important in optical 'etching.'

Expo-sures from strong light sources can be used to

chemi-cally alter substrate materials through a template

mask so that some of the materials are removed and

some remain In this manner, mercury arc lamps have

been used in the semiconductor industry for circuit

design through optical lithography This is a

technol-ogy that may someday be superseded by

higher-pre-cision electron-beam and laser etching techniques

ArchieNetwork archiving software developed by

Peter Deutsch, Alan Emtage, and Bill Heelan Named

for the word archive, Archie is an Internet query tool

that tracks the contents ofanonymous ftp sites It was

introduced at McGill University, Canada, in 1990

Archie allows users to retrieve a list ofFTP locations

by submitting file search criteria to an Archie server

See Veronica

Archimedes(ca 287-212 BC)AGreek

mathemati-cian and inventor born in Sicily who made contribu-tions to our understanding of volume and displace-ment, and who created the mathematical treatise

"Measurement of the Circle" in which he described the calculation ofthe ratio ofa circle's circumference

to its radius See Archimedes' principle

Archimedes' principleAbody immersed in fluid is buoyed up by a force equal to the weight of the fluid displaced (This principle is humorously illustrated

by actor Gary Oldman in a bathtub in the Cinecom Entertainment movie production of "Rosencrantz and Guildenstem Are Dead.")

architectOne who designs a layout or topology, such

as a building layout, circuit board architecture, net-work routing system, etc The architect frequently is also the one who drafts the technical drawings asso-ciated with the layout and mayor may not check elec-tronics codes, building codes, or other regulations as-sociated with the design

architectureThe design and layout ofa process, sys-tem, or facility The architecture involves the overall plan and topology, in addition to the relationships and interconnections between the individual parts It may

also include the direction of information paths or

movement within the system Good architectures usu-ally try to incorporate, or at least balance, flexibility, robustness, efficiency, and scalability, whether it be the design of a building or of a microprocessor chip See topology

archivalAformat, medium, or protective system de-signed to facilitate preservation Archival papers and plastic sleeves are acid-free, or free of plastics that may change the information or degrade rapidly Ar-chival data storage formats are nonvolatile (magnetic media such as video tapes, audio tapes, floppy dis-kettes, etc are not very stable over time and may be damaged by proximity to magnets) and resistant to damage and degradation In the data industry, archi-val file formats are as important as the materials on which they are stored, as the information is useless

if it can no longer be read or deciphered

archiveA repository of records or files A backup or duplicate ofinformation made to preserve or prevent loss in compressed or uncompressed form.ADarchive generally contains information that needs to be kept over time, for one reason or another (legal, histori-cal, etc.) Many archives are seldom or ever accessed Computer data archives are becoming more preva-lent and offer many search and retrieval advantages over traditional paper-based archives See anony-mous FTP, Archie, archival, FTP

archiverAterm for software tools that are designed

to store files in such a way that they take a minimum

of space and can be retrieved, reconstructed, and viewed at a later date Software archivers often in-clude compression algorithms and switches to allow

an archived file to be scanned for header informa-tion without decompressing it The degree of com-pression possible is very dependent upon the inter-action between the type of compression algorithm and the type ofdata being compressed Common soft-ware archivers include zip, lharc, Stuffit, andtar.

pressed or uncompressed, encoded or not encoded,

such that it can be accessed and viewed at some

fu-ture date, if needed Archiving involves selecting a

storage fonnat, medium, and location and carrying

out occasional or scheduled consolidation and

orga-nization ofthe objects or information One ofthe big

issues with archiving, besides space, is the

develop-ment of efficient search and retrieval methods that

make it possible to find a desired piece of

infonna-tion in a vast amount of data See archival, archive,

database, FTP

ARCnetAttached Resource Computernetwork.A

popular pioneering local area network (LAN)

devel-oped by Datapoint Corporation in 1977 for use with

thin coaxial cable Incorporating a modified

Token-Ring passing scheme, ARCnet provides high-speed

baseband communications at 2.5 Mbps with either a

bus or star topology ARCnet became standardized

as ANSI 878.1 Although not as widespread as it once

was, ARCnet has been upgraded to include

transmis-sion over copper twisted pair wire and fiber optic

cables

ArcstarThe brand name for the Nippon Telegraph

and Telephone Corporation's (NIT) global services

including NTT Worldwide Telecommunications

Cor-poration, NTT Europe, ntta.com and Asian branches

These include managed bandwidth, Frame Relay, and

Internet Protocol (IP) virtual private networks

(VPNs) See Nippon Telegraph and Telephone

Cor-poration

ARD 1 advanced research and development 2 See

Automatic Ring Down

ARIADNEt TheARIADNEnetwork, an academic

and research network operated out ofAthens, Greece

by NCSR Demokritos, a physics and sciences

re-search association http://www.ariadne-t.gr/

Ardire-Stratigakis-Hayduk algorithmASH A

lossless compression algorithm, named after its

cre-ators at Western DataCom, developed between 1990

and 1993.Itwas intended for use over synchronous

data communications with varying media

character-istics Unlike asynchronous transmissions protocols,

framed data can contain a very large number of bits

and does not have to be timed with start and stop bits

ASH provides a means to provide good compression

ratios on various types of traffic in a multiuser

net-work

ASH incorporates interesting concepts from artificial

intelligence By using pattern-matching and

predic-tive algorithms, data not yet transmitted and

noniden-tical strings can be processed and evaluated As part

of the compression methodology, ASH uses an

Oc-currence Optimized Codebook (DOC) for fast-cache

access to commonly occurring tokens and strings

ASH safeguards against data expansion and latency

Apatent has been sought for the ASH technology See

Lempel-Ziv-Welch

ARDIS A commercial packet-switched nationwide

wireless data communications service developed in

the mid-1980s by Motorola and International

Busi-ness Machines (IBM) and now owned by Motorola

is appropriate for short messages and quick database lookups for a variety ofapplications ARDIS is some-what similar to CDPD except that it is a data-only service It is used for wireless faxing and realtime messaging with any Internet address worldwide ARDIS can be accessed through laptops, and per-sonal data assistants See RAM Mobile Data ARE See all routes explorer

area codeA three-digit code in a phone number that designates the region See North American Number-ing Plan (NANP) See the Appendix for a chart area code restrictionAservice for enabling the sub-scriber to deny telephone calls to specified area codes

It is not a blanket restriction as in some long-distance call-blocking services The service is useful in offices and other environments where it is othetwise diffi-cult to monitor phone use

area networkSee local area network, metropolitan area network, wide area network

Area of ServiceADS The geographical area sup-ported by a vendor, carrier, or service provider Arena1 The name of an HTML3 browser from the World Wide Web Consortium (W3C) designed as a proof-of-concept demonstration tool for HTML+ ideas preceding HTML3

ARES See Amateur Radio Emergency Service ARF See Alternate Regulatory Framework argon(symb - Ar) Argon is a colorless, odorless gas

used in light bulbs Argon plasma arc lamps can pro-vide a continuous radiation source covering a broad spectrum from ultraviolet to infrared suitable for test-ing solar energy components for use in satellite com-munications See argon laser

argon laserA type of gas laser that primarily uses argon gas This common type of laser can be used to produce green and blue light, which is useful for cre-ating laser light show effects.Itis similar to a kryp-ton laser, except that argon produces a little more light Argon is sometimes combined with krypton gas to produce an argon-krypton hybrid Argon la-sers are typically water-cooled

ARI Automatic Room Identification A telephony service used especially in the hotel/motel industry to identify call locations

ARm See Association ofRadio Industries and Busi-nesses

AriellHistorically, the first U.K satellite project to study the ionosphere, launched in April 1962 The satellite's orbit decayed in 1976

ARIES 1 Angle-Resolved Ion and Electron Spec-troscopy 2 The name of a commercial satellite ser-vice See Constellation Communications, Inc 3 See Australian Resource Information and Environment Satellite

ARINC-429 Digital Information Transfer System DITS DITS is a digital point-to-point hardware ar-chitecture and data specification for describing a digital bus for device communications for the aeronautics industry The transmission hardware is based upon twisted-pair wires with one transmitter connected to one or more receivers The data protocol is based

Fiber Optics Illustrated Dictionary

upon 32-bit words consisting of a data portion and a

label identifying the nature ofthe data Development

of the DITS specification and ARINC-compatible

products aided in the commercialization of digital

communications for aeronautics devices and

facili-tated the development ofmodular,

off-the-shelfprod-ucts See ARINC-629

ARINC-629A commercial civilian communications

protocol based upon a central twisted-pair bus

archi-tecture which can accommodate up to 120 peripheral

devices or terminals at a 2-MHz bus rate

ARINC-629 evolved from ARINC-429, which was developed

in the 1970s ARINC products are manufactured by

Excalibur Systems, Inc

ARINC IncorporatedAnorganization formally

es-tablished in 1929 by Louis Caldwell and

representa-tives offour major airlines as Aeronautical Radio, Inc

ARINC was established to be the dominant

nongov-ernment single licensee and coordinator ofradio

com-munications Upon its formation, the Federal Radio

Commission (FRC) transferred to ARINC the

respon-sibility for aeronautical ground radio stations, thus

providing a within-the-industry means

ofadministrat-ing aeronautic rules and regulations established by

theFRC

ARINC continues to coordinate airline industry

tele-communications activities, tele-communications, and

in-fonnation processing systems It publishes standards

ofrelevance to avionics systems and analog and

digi-tal equipment

ARISE 1 See Advanced Radio Interferometry

be-tween Space and Earth 2 American Renaissance in

Science Education 3 Applications Reform in

Sec-ondary Education

ARISSSee Amateur Radio International Space

Sta-tion

Aristote AssociationA French association of

orga-nizations and frrms engaged in the development of

telecommunications and data transmissions

technolo-gies The Secretariat is located at the Ecole

Polytechnique in Paris, France, with seminars and

workshops held at the Arago and Poincare

amphithe-aters http://www-aristote.cea.fr/

ARISTOTELESApplications and Research

Involv-ing Space Technologies/Techniques ObservInvolv-ing the

Earth's Fields from Low Earth-Orbiting Satellites A

joint project of NASA and ESA carrying out

scien-tific research data gathering on the Earth's gravity and

magnetic fields It is equipped with a Global

Posi-tioning Service (GPS) receiver, gradiometer, and

sca-lar magnetometer

ArkayCT-650 A commercial computer based upon

a description of a paperclip computer, (a homebrew

digital computer that could be constructed out of

materials found around a home)

ARL 1 Air Resources Laboratory (NOAA)

http://www.arl.noaa.gov/ 2 See Association of

Re-search Libraries

armatureA portion of a magnetic circuit typically

consisting of a conducting material, such as wire,

wound around a core, which is moved within a strong

magnetic field to create current If the armature

revolves, the wound material interacts with the mag-netic lines offorce, in a sense, cutting in and out, and the current generated by this interaction can be drawn out The arrangement is used in generators and alter-nators, where the current may be drawn out by brushes See coil

Armed Forces Communications and Electronics AssociationAFCEA An international nonprofit professional association for communications, elec-tronics, and intelligence Founded in 1946, the asso-ciation has over 40,000 individual and corporate members in government, industry, and military sec-tors AFCEA publishes SIGNAL Magazine, techni-cal papers, and books http://www.afcea.org/ ARM See American Radio Museum

armor1 Defensive or protective covering 2 Atype ofheavy-duty waterproofing or other shielding used especially in underwater or underground installations

3 Heavy shielding to protect facilities, equipment, and personnel from radiation or chemical contami-nation 4 In computer technology, heavy security measures taken to keep users offa system, which may range from inaccessible facilities to extra software measures taken to discourage unauthorized intrusion armor-platedA physical or administrative high se-curity system which the administrators deem to be virtually impenetrable Highly resistant to access or tampering Bullet-proof

armored cableSee aramid yarn; cable, annored armoring, ballisticAstrong armor layer (e.g., coated steel) used to protect aerial components and cables from shotgun pellet intrusion Ballistic annoring for fiber optic cables is generally about 0.25mInthick Sometimes dual armoring layers are used, in addi-tion to aramid fibers

The ballistic energy from pellets hitting a cable is dis-sipated by the steel armoring Increased protection against larger pellets is offered by aramid fibers that cushion the fibers from the impact of a pellet ZETABONTM is an example ofa steel-annored cable distributed by Dow Chemical Company See aramid; cable, armored

Armstrong, Edwin Howard(1890-1954) A gifted American researcher who invented the superhetero-dyne circuit and frequency modulation (FM) Arm-strong was not only a good inventor but also a good theoretician; he was one of the few people who un-derstood, on a physics level, many of the new inven-tions that were making possible the development of wireless communications

In October 1914, Armstrong was awarded a patent for his wireless receiving system (U.S #1,113,149)

Inthe 1920s, he contested Lee de Forest in the in-vention of regeneration, but de Forest won the suit After many years ofpainstaking research against con-ventional wisdom and the negative predictions of mathematicians and engineers, Armstrong proposed

a method of wave modulation that varied the fre-quency rather than the amplitude of a wave He was awarded a patent for FM radio signaling in Decem-ber 1933 (U.S #1,941,066)

Armstrong waged a long and tragic legal battle with

were posthumously upheld in his favor During World

War II, Armstrong furthered the art ofradar

transmis-sion by suggesting the use ofFM signals, rather than

the short pulse radar bursts that were used at the time

His ideas are now commonly incorporated into

fre-quency modulated (FM) radio, television, and radar

transmissions See frequency modulation, heterodyning

AROS I Amateur Radio Observation Service

2 Amiga Research OS Aproject initiated in the

mid-1990s to update, bug-fix, and enhance the Amiga

Operating System http://www.aros.org/

ARPSee Address Resolution Protocol

ARPAAdvanced Research Projects Agency See

Defense Advanced Research Projects Agency

ARPANETAdvanced Research Projects Agency

Network The historical basis ofthe Internet,

ARPA-NET was originally discussed by the ACM in 1967,

presented to ARPA the next year and put into

opera-tion in 1969 The frrst widespread demonstraopera-tion of

ARPANET occurred at a Computer Communications

conference in 1972, and a year later ARPANET

traf-fic had grown to millions ofpackets of data transfer

per day By 1975, the ARPANET had been transferred

to the Defense Communications Agency (later the

Defense Information Systems Agency)

In1982, ARPA endorsed TCP/IP as its protocol suite

In 1983, ARPANET split into MILNET and

ARPA-NET (mandated to use TCP/IP), which together

formed the Internet Each was given a network

num-ber, and gateways were installed to provide packet

forwarding between them ARPANET was officially

discontinued in 1990, largely due to the evolution of

the Internet See ARPA, BITNET, lANA, NSFNET,

NEARNet, SPAN

ARQ See automatic retransmit request

arrayA type of data organization structure

com-monly used in programming.Anarray consists ofan

ordered list or matrix of information which can be

visualized as 2D or 3D tables of information

con-tained in cells which often have common

character-istics, such as the size of the data cell (although the

data in the cells may vary in length) Arrays form the

structural basis for many types of databases,

includ-ing tables and lists Many software programs have

built-in array-handling functions to automate

com-mon ways in which arrays are manipulated

array antenna I.Anantenna with a number of

di-recting, reflecting, or other elements arranged in a

more-or-Iess regularly spaced, often symmetrical

pattern See antenna 2 One antenna in an array of

antennas that are organized and connected in such a

way as to significantly boost power, range, and

per-formance These powerful antenna systems are used

for picking up weak signals as in astronomy and

mili-tary applications

ARRLSee American Radio Relay League

ARRL Monitoring SystemApolicing system ofthe

American Radio Relay League to monitor and

main-tain the correct, licensed, and responsible use

ofama-teur radio frequencies and procedures For the most

part, the amateur radio community successfully seeks

thorized use reaches problematic levels or originates

in countries that are not regulated by the U.S Fed-eral Communications Commission (FCC), at which time the ARRL will document the problems and call for assistance from appropriate domestic and inter-national agencies See American Radio Relay League

ARRNAmateur Radio Repeater Network

ARSSee Automatic Route Selection

ARSRSee Air Route Surveillance Radar

articulationClear utterance or playback of sounds

- the degree to which reproduced or transmitted sounds are clear enough to be understood by a lis-tener Mumbling is poor speech articulation When people say "Testing, testing, " on a sound system, they are testing not only circuit functioning and vol-ume but also the clarity of the sound and capability

of conveying a message Articulation does not have

to be high fidelity to be understood It depends in part upon the ability of the recipient to perceive and un-derstand the message, and may not have to match perfectly the original This is an important aspect of data communications as well When conversations are converted from analog to digital, through a pro-cess called sampling and quantization, it is important

to determine how much ofthe information is needed

in order for the communication to be understood by the recipient This information can be applied to com-pression and decomcom-pression systems for speeding up transmissions See fidelity, intelligibility

articulation indexAI A scale from 0 to 1 that pro-vides an objective reference for the intelligibility of voice signals expressed AI is quantified in terms of the percentage of speech units understood by a lis-tener when the units are presented out ofcontext The index is a useful measure for testing and comparing voice transmission and speech compression/decom-pression technologies See articulation

artificial intelligenceAI Insights or behaviors at-tributed to an entity, usually a machine, that is not traditionally perceived by humans as having the ca-pability to think in ways that involve problem-solv-ing, insight, and other uniquely human characteris-tics The field of artificial intelligence has spawned many useful approaches, languages, techniques, and programming algorithms Expert systems, neural net-works, robotics, vision systems, and natural language processing all have their origins in AI research People interested in artificial intelligence come from

a diverse range of backgrounds

The origins of artificial intelligence, as they apply to computers, trace back to the 1950s, thoughAda Love-lace proposed in the 1800s that "thinking machines" could be programmed to create music or art Pioneer researchers include A Turing, J McCarthy, and N Wiener See expert systems; Intelligent Networks; Lovelace, Ada; robotics

Artronartificialneuron The familiar name for an

electronically simulated neuron used in a maze-run-ning robotic mouse in the early 1960s See Melpar model, neural network

Fiber Optics Illustrated Dictionary

AS1 See Applicability Statement 2 See

autono-mous system

as isA tenn applied to products that are bought and

sold with no implied or stated warranties Condition

may be guessed by inspecting and trying the

equip-ment, but there is no way to know the completeness,

remaining useful life, or technical functionality ofthe

equipment See fair, good

AS&C1 Advanced Systems&Concepts Adivision

of the U.S Department of Defense associated with

the Deputy Under Secretary of Defense (DUSD)

ASCO, the DTRA Advanced Systems & Concepts

Office, encourages seed projects for technologies

developed to counter threats to national security 2

Alann Surveillance and Control

AS-Interface,Actuator Sensor Interface, AS-i An

open network protocol for automating actuator and

sensor control for industrial applications It can

op-erate as a controller or as a stand-alone automation

support bus It may also be used with higher level

field buses to enable remote input/output operations

A single AS-i v2.0 master can support up to 124

ac-tuators/outputs and 124 sensors/inputs See actuator,

INTERBUS, PROFffiUS

ASA1 See Acoustical Society ofAmerica 2

Assis-tant Secretary of the Army

ASARSSee Advanced Synthetic Aperture Radar

System

ASC 1 advanced switching communications

2 Aeronautical Systems Center A U.S facility

lo-cated at Wright-Patterson AFB Science and

technol-ogy programs are carried out in the Wright and

Arm-strong Laboratories

Ascend Inverse MultiplexingAIM An in-band

net-working protocol from Ascend Communications that

manages interconnections between two remote

in-verse multiplexers

Ascend Password ProtocolAPP A network User

Datagram Protocol (UDP) used in servers to respond

to password challenges from external authentication

servers APP Server utilities are available from

As-cend for a wide variety of computer platforms

ASAISee Adjunct Switch Application Interface

ASAPIAdvanced Speech API.Anopen,

cross-plat-fonn speech applications programming interface

de-veloped by AT&T

ASCASee Advanced Satellite for Cosmology and

Astrophysics

Ascend Password ProtocolAPP AUser Datagram

Protocol (UDP) network security protocol defaulting

to port7001.

ascending nodeIntersection of a satellite's orbital

plane with the Earth's equatorial plane

Ascn(as-kee) The American Standard Code for

In-formation Interchange was developed by the

Ameri-can National Standards Institute (ANSI) Also known

as ASCII International Telegraph Alphabet 5, ASCII

is the most widely used computer character set

en-coding scheme currently employing seven bits, thus

making a total of 128 possible characters/symbols

ASCII is mainly suitable for English language

com-munications Since it is very limited in its letters and

symbols, many extensions to ASCII have been incor-porated into key mappings on various computers to include symbols and western European characters Sometimes called extended ASCII (even though the extensions aren't standardized), these 8-bit encodings provide 256 possible characters, but the higher 128 characters are not usually compatible across plat-forms See EBCDIC, Unicode See the Appendix for

an ASCII chart

ASCn editorA text editing tool that handles basic, simple characters standardized as ASCII text, which are cross-compatible and transferable over almost all seven-bit-compatible systems, which includes most computer networks Since the ASCII standard does not support style attributes (bold, underline, oblique, etc.), it cannot be used for extensive formatting Due

to the limitations and simplicity of its character set, ASCII editors are very fast They are also good for writing computer source code, which typically needs speed and compatibility more than style tags

If you require style tags and indentation for text for-matting, and want to transfer the documents across applications or platforms, the best supported format that includes them is Rich Text Fonnat (RTF), also known as Interchange Format (developed by Micro-soft and supported across its products) It's not 100% compatible across platforms, but it's pretty close and can be read and written by most word processors (with import and export menu options) Another good format for transferring more complex documents is generic Adobe PostScript, which includes not only text and style support, but image positioning, layout effects and more, or its cousin, Adobe Acrobat's Por-table Document Format (PDF)

When designing Web pages with links to download-able files, there should be more than one format avail-able If all Web site managers were to include these three: an ASCII version, an RTF version (which can

be read into virtually any popular word processor), and a PostScript or PDF version, then the needs of low-end and high-end users would be well met, and

at least one of the files would be accessible to virtu-ally everyone using the Web See appendix for an ASCII chart

ASDSPapplication-specific digital signal processor See digital signal processor

ASEApplication Service Element An element ofan application layer protocol in the Open Systems in-terconnection (OSI) layered network model.Itis combined with other elements to form the complete protocol See Open Systems Interconnect

ASFPSee Application Specific Fiber Platform ASHSee Ardire-Stratigakis-Hayduk

AsiaDABCommittee, AsiaDAB ADC Anonprofit association working in conjunction with the World DAB Forum to promote, support, and coordinate the implementation ofdigital radio broadcasting tech-nologies in Asia Digital Audio Broadcasting (DAB) promises to significantly change and improve the quality and richness of programming information available to consumers See Digital Audio Broadcast-ing Forum http://www.asiadab.org/

based mobile phone system of Asia-Pacific Mobile

Telecommunications Satellite Pte Ltd The system

was supplied by Hughes Space and Communications

International, Inc It operates in the L-band to

pro-vide a mobile infrastructure for communications in

Asian-Pacific regions from Japan to Pakistan Asia

is a world leader in many aspects of wireless

com-munications

ASI1 Advanced Study Institute 2 artificial

sens-ing instrument 3 Astronomical Society of India

ASICSee application-specific integrated circuit

ASKSee amplitude-shift keying, modulation

Ask JeevesA prominent and specialized freely

ac-cessible search engine on the Web, Ask Jeeves uses

natural language processing to search information

based upon sentence-like queries

Finding information on the Internet can be a

daunt-ing prospect and many lexical search engines search

on keywords or conditional statements and provide

thousands or millions of hits on the queried topic In

contrast, Ask Jeeves will parse out English-like

que-ries and provide a selective group of good hits from

a variety of search sources based upon intelligent

search algorithms, a process central to data mining

See data mining; search engine, Web See appendix

for a search engine chart

ASLAdaptive Speed Leveling AU.S Robotics

mo-dem term for adjusting the speed ofa serial

transmis-sion, depending upon line conditions, to optimize the

transfer of data

ASN1 Abstract Syntax Notation See ASN.l 2 See

Autonomous System Number

ASN.lAbstract Syntax Notation 1.AnISO/ITV-T

standard machine- and implementation-independent

language defined in 1988 for the description of data,

to facilitate the exchange of structured data among

applications programs ISO 8824, lTV TS X.208

ASP1 Abstract Service Primitive In ATM

network-ing, an implementation-independent description of

user/provider interactions, as defined by the Open

Systems Interconnection (OSI) 2 Adjunct Service

Point A network feature of peripherals designed to

respond intelligently to processing requests 3

admin-istrative service provider SCSA term 4 analog

sig-nal processing 5 See AppleTalk Session Protocol

6 See Application Service Provider 7 See ATM

switch processor 8 Attached Support Processor

9 Association of Shareware Professionals

ASP Industry ConsortiumAninformational global

advocacy group supporting Application Service

Pro-viders (ASPs), their delivery associates, and their

customers, founded in May 1999 The group provides

research information, education, and strategic

guid-ance The ASP Consortium currently serves hundreds

of members in more than two dozen countries It is

managed by Virtual, Inc., a high-tech industry

inte-grated management and marketing firm

http://www.aspconsortium.org/

aspect ratioThe relationship of the proportions of

the width to the height, usually ofa rectangular form

A two-to-one aspect ratio, for example, is commonly

monitors are similar, but cinematic films, which are shown in theaters with panoramic screens, have a much greater width-to-height ratio This is why letterboxed films have a dark strip on the top and bottom to preserve the full width of the image Unletterboxed films have been modified to remove part of the picture from the sides See anamorphic ASPISee Advanced SCSI Programming Interface ASQ1 Administrative Science Quarterly 2 Ameri-can Society for Quality ASQ sponsors ASQNet http://www.asq.org/http://www.asqnet.org/3 Appli-cant and Student Query A system to automate the verification ofstudent admissions information 4 Ap-plication Status Query A Web-based tool for allow-ing applicants to check their status, developed by DLAHROC http://www.hroc.dla.mil/5 Automated Status Query

ASR1 Access Service Request A request sent to a local exchange carrier (LEC) for access to the local circuit 2 See Airport Surveillance Radar 3 Auto-matic Send/Receive A system that can send and re-ceive messages unattended 4 See Automatic Speech Recognition

assemblerAprogram that converts symbolic assem-bly language program code into machine instructions that can be directly executed by a computer CPU On early microcomputers, in the 1970s, most serious pro-gramming was done with an assembler

assembly languageAlow-level symbolic computer language which structurally and mnemonically fits somewhere between machine code and higher level languages such as C, BASIC, Java, and Perl Lan-guages like BASIC and Perl are typically run in in-terpreted mode (although compilers exist for almost everything, if you really want one) When compiled and assembled, C and assembly language are verted into machine language, which typically con-sists ofthe binary digits one and zero and is very dif-ficult (for normal folks) to read and debug

By coding in assembly language (which is difficult for most folks) and then using an assembler, a soft-ware utility to convert to machine code, the program can often be optimized to run faster and may be more difficult to reverse-engineer See symbolic code assigned frequencySee Federal Communications Commission

assigned numbersA sequential numbering system administrated by IANA to organize and assist in the search and retrieval ofRequest for Comments (RFC) documents See lANA, Request for Comments Association Control Service ElementACSE An

International Standards Organization (ISO) applica-tion layer service for establishing a connecapplica-tion, as part

of the Open Systems Interconnection (OSI) model Association for Computing MachineryACM A well-known trade association serving more than 80,000 computing professionalsinover 100 countries Members participate in the exchange of ideas, dis-coveries and information in many areas ofacademia, government, and industry The ACM was founded in

1947 http://www.acm.org/

Fiber Optics Illustrated Dictionary

Association for Cooperation in

Telecommunica-tions Research in Switzerland ACTRlS A

telecom-munications research initiative for precompetitive

research in telecommunication technologies, formed

in 1995 by the Pro Telecom partners, an association

ofSwiss telecommunications companies ACTRIS is

centered in the Multimedia Communications Lab in

Basel, Europe's largest experimental platform It

serves major Swiss telecom companies, as well as

those in neighboring countries The main objectives

are to promote research and education in

telecommu-nications

Association for Education in Journalism and Mass

Communication AEJMe Aprofessional association

of post-secondary journalism and mass

communica-tions educators and administrators

http://www.aejmc.sc.edu/

Association for Educational Communications and

Technology AECT An organization committed to

providing communication among professionals with

a common interest in using technology for education

http://www.aect.org/

Association for Information and Image

Manage-ment AIIM International AIIM was established in

1943 as the National Microfilm Association It

sup-ports users of document and content technologies

with information about technologies and suppliers

AIIM seeks to provide practical, unbiased educational

information to its global membership through

con-ferences, articles, and member participation

http://www.aiim.org!

Association for Information Systems AlS A

pro-fessional organization serving as a global resource for

academics specializing in information systems,

founded in 1994 AlS publishesThe Journal of the

AIS and The Communications ofthe Association for

/nfo177zation Systems http://www.aisnet.org/

Association for Interactive Media AIM A

Wash-ington, D e.-based nonprofit trade association

dedi-cated to promoting consumer confidence and

govern-ment support of interactive media products and

re-lated technologies http://www.interactivehq.org!

Association for Literary and Linguistic

Comput-ing ALLe An association for supportComput-ing the use of

computer technologies for studying languages and

literature, founded in 1973 ALLC publishes the

Lit-erary and Linguistic Computing journal through

Ox-ford University Press The association sponsors an

annual convention in cooperation with the

Associa-tion for Computers and the Humanities (ACH)

Association for Maximum Service Television

MSTY Aprofessional association of local television

stations established in 1956 to undertake studies to

support development of Federal Communications

Commission (FCC) television technical standards In

1962, MSTV provided a voice for new television

technologies in the All-Channel Receiver Act In

1987, the association brought together broadcast

or-ganizations to petition the FCC to look into

high-defi-nition television (HDTV) and participated materially

in the Advisory Committee on Advanced Television

Services (ACATS) In 1996, the Consumer Electronics

Manufacturers Association (CEMA) and MSTV cre-ated the Model HDTV Station Project, licensed as WHD-TV, to educate broadcasters on the implemen-tation of digital television services

MSTV seeks to preserve and improve the technical quality of free, universal, community-based televi-sion service to the American public MSTV provides its members with information on new technologies and policies, particularly digital television advance-ments and implementation information See Ad-vanced Television Test Center, Advisory Committee

on Advanced Television Services, Digital Television Station Project, Inc http://www.mstv.org!

Association for Women in Computing AWe A not-for-profit professional association founded in 1978

to promote the advancement of women in comput-ing http://www.awc-hq.org!

Association of College and University Telecommu-nications Administrators ACUTA An international nonprofit educational association serving colleges and universities and representing vendors serving the educational market ACUTA sponsors the award for Institutional Excellence in Telecommunications and publishes news and a quarterly journal

http://www.acuta.org!

Association of Communications Technicians ACT

An organization to support technicians working in the field of communications ACT is a member of the PClAFederation ofCouncils, representing commer-cial and private mobile radio service communications industries

Association of Competitive Telecommunications Suppliers ACTS A Canadian-based association rep-resenting telecommunications equipment manufac-turers and suppliers in order to support and encour-age market competition

Association of Computer Professionals ACP A U.K.-based nonprofit organization providing courses that lead to recognized qualifications, founded in

1984 http://www.btinternet.com!-acp/

Association of Computer Support Specialists ACSS A trade organization assisting and represent-ing those who install, support, maintain, test, and re-pair computing systems Members include vendors and manufacturers who provide customer support, as well as independent consultants and those who pro-vide equipment and services to support these special-ists http://www.acss.org/

Association of Computer Telephone Integration Users and Suppliers ACTIUS A trade organization

in the United Kingdom which promotes awareness and acceptance of computer-telephone integration (CTI) technology through campaigns and educa-tional programs

Association ofIndependents in Radio AIR A non-profit organization representing and promoting the interests of a diverse membership of audio produc-ers, audio artists, radio broadcast stations, and me-dia arts centers AIR sponsors online discussion groups, group health benefits, and theAIRSPACE

journal See Producers Advocacy Group

http://www.airmedia.org!

ARIB A research and development organization,

headquartered in Tokyo, Japan, that studies radio

waves and developing radio systems and industries

in telecommunications and broadcasting, in order to

promote public welfare A number of committees

work under ARIB, including the Infrared

Communi-cations Systems Study Committee

Association ofResearch Libraries ARL.

Anot-for-profit organization of the leading research libraries

in North America TheARLfurthers and promotes

the evolution ofresearch libraries and scholarly

com-munication http://www.arl.org/

Association of Science-Technology Centers

Incor-poratedASTC.Anorganization of science centers

and museums dedicated to fostering the public

un-derstanding ofscience through innovation and

excel-lence ASTC was founded in 1973 and has members

worldwide in more than three dozen countries

http://www.astc.org/

Association ofWireless System IntegratorsAWSI

Anorganization to support integrators working in the

field of wireless communications ACT is a member

of the PCIA Federation of Councils, internationally

representing commercial and private mobile radio

service communications industries

ASSP 1 acoustics speech and signal processing

2 application-specific standard product An

inte-grated circuit designed for a specific application

ASSP MagazineA publication of the IEEE devoted

to signal processing

ASSTASee Australian Speech Science and

Technol-ogy Association Incorporated

Assured LinkA telephone link meeting certain

mini-mum transmission, loss (5.5dBin the 300- to

3000-Hz bandwidth range), and service standards for a

communications circuit for voice grade analog

sig-nals and sometimes one-way digital sigsig-nals See

Ba-sic Link

ASTSee Automatic Scheduled Testing

astatic galvanometerA device developed by

Will-iam Thompson (Lord Kelvin) in 1858 to overcome

the limitations of earlier instruments that were

sub-ject to interference from the Earth's magnetic field

Unlike previous galvanometers employing one

needle, the astatic galvanometer uses two needles,

each with a separate coil The needles are oriented

so that north and south poles effectively cancel out

the Earth's magnetic interference See galvanometer

ASTC I See Association of Science-Technology

Centers 2 Australian Science and Technology

Coun-cil An association ofprofessionals involved in

tech-nical and business communications.3.Australian

Society for Technical Communication Inc A

non-profit society of professionals involved in

commu-nicating technical information

ASTERAdvanced Spaceborne Thermal Emission

and Reflection Radiometer A Jet Propulsion

Labo-ratory (JPL) satellite imaging instrument project

Since 1998, ASTER has been obtaining moderate to

coarse detail maps of Earth's temperature,

emissiv-ity, reflectance, and elevation characteristics The

part of NASA's Earth Observing System (EOS) The ASTER instrument was subsequently launched

in December 1999 aboard Terra to provide high spa-tial resolution instruments as one offive sensing sys-tems See Earth Observing System See the NASA ASTER Web site for information on ASTER's progress http://asterweb.jpl.nasa.gov/

astigmatism Anaberration associated with lenses in which irregularities in the shape or general curvature

of the lens cause more than one line of focus or in which a portion of the preferred line of focus is blurred

Astigmatism is inherent in a number of laser beam-generating technologies such as laser diodes Since the semiconductor-based emission facet of a laser diode is typically rectangular, it causes an astigmatic beam (a beam with an elliptical cross-section) that is usually corrected with one or more lenses

ASTRALAlliance for Strategic Token-Ring Ad-vancement and Leadership A vendsupported or-ganization formed in the mid-I 990s to support mi-gration to High Speed Token-Ring LAN technology The group prepared a number of white papers and a draft standard for 100 Mbps Token-Ring transmis-sions With the emergence of Ethernet as a widely-adapted technology, interest in Token-Ring networks was waning in the late-1990s See High Speed To-ken-Ring

Astro-DSee Advanced Satellite for Cosmology and Astrophysics

AstrolinkA commercial global satellite communi-cations service scheduled to come online in 2001 Astrolink International Limited is an independent Lockheed Martin venture Lockheed Martin has been active in global communications frequency utiliza-tion conferences and on various ATM- and lTU-T-related technical and standardization committees and working groups

Astrolink is targeted at providing multimedia appli-cations over virtual private networks (VPN) with a focus on secure transmissions and connectivity be-tween private and public networks

The Astrolink system consists of nine geostationary satellites: five to provide global coverage, four to come online later They will be operating over

Ka-band frequencies with approximately 6-Gbps capac-ity per satellite using continuous beam uplinks and multifrequency TDMA

astronomical unitAU A unit of length defined as the distance from the Earth to the Sun, a measure that

is generally given as about 149,579,000 to 149,599,000 kilometers The variation in the unit comes about due to the variation in the Earth's move-ment in relation to the Sun and the measuring sys-tem and criteria used to establish the distance ASUapplication-specific unit

asymmetric1 Not symmetric, lopsided, irregularly proportioned, unbalanced, one-directional, having one side larger or longer than the other

Asymmetric Digital Subscriber LineADSL.Adata communications service over traditional phone wires